package cn.nju.zyy.share.atomic;

import java.util.Timer;
import java.util.TimerTask;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

// Reuses storage so we don't run out of memory
class CircularSet {
	private int[] array;
	private int len;
	private int index = 0;
	
	public CircularSet(int size) {
		array = new int[size];
		len = size;
		// Initialize to a value not produced by the SerialNumberGenerator:
		for (int i = 0; i < len; i++) {
			array[i] = -1;
		}
	}
	
	public synchronized void add(int i) {
		array[index] = i;
		// Wrap index and write over old elements:
		index = ++index % len;
	}
	
	public synchronized boolean contains(int val) {
		for (int i = 0; i < len; i++) {
			if (array[i] == val) return true;
		}
		return false;
	}
}

public class SerialNumberChecker {
	private static final int SIZE = 10;
	private static CircularSet serials = new CircularSet(1000);
	private static ExecutorService exec = Executors.newCachedThreadPool();
	
	static class SerialChecker implements Runnable {
		@Override
		public void run() {
			while (true) {
				int serial = SerialNumberGenerator.nextSerialNumber();
				if (serials.contains(serial)) {
					System.out.println("Duplicate: " + serial);
					System.exit(0);
				}
				serials.add(serial);
			}
		}
	}
	
	public static void main(String[] args) throws Throwable, InterruptedException {
		for (int i = 0; i < SIZE; i++) {
			exec.execute(new SerialChecker());
		}
		// Stop after n seconds if there's an argument:
		// or terminate after 3 seconds
		if (args.length > 0) {
			TimeUnit.SECONDS.sleep(new Integer(args[0]));
			System.out.println("No duplicates detected");
			System.exit(0);
		} else {
			new Timer().schedule(new TimerTask() {
				public void run() {
					System.out.println("Aborting");
					System.exit(0);
				}
			}, 3000);
		}
	}
}
